1. Field of the Invention
The present invention relates to a substrate processing apparatus and a method for detecting an abnormality of an ozone gas concentration.
2. Description of the Related Art
As disclosed in Japanese Laid-Open Patent Application Publication No. 2011-5360, a technique is known of determining a state of a device for generating ozone gas or a device for decomposing ozone gas by using an ozone concentration detected by an ozone sensor. In Japanese Laid-Open Patent Application Publication No. 2011-5360, whether the device for decomposing ozone gas comes to the end of its life is determined by detecting an ozone gas concentration supplied to the device by the ozone sensor and by determining whether a proper amount of ozone gas is supplied to the device.
However, in Japanese Laid-Open Patent Application Publication No. 2011-5360, the determination is wrong when the ozone sensor does not work normally and the detected ozone gas concentration is not a normal value, which causes trouble. In particular, regular maintenance of the ozone sensor has to be performed, for example, once a day, which is so frequent that actual implementation of the maintenance is often difficult.